Optical fibers have long been the backbone of modern communication system. One way of extending the capability of optical fibers is to thin down the core sizes as microfiber which facilitates light-matter interaction through evanescent light. Among different microfiber based structure, the microfiber knot resonator (MKR) is a resonant structure which finds applications in lasing, filtering and optical switching <sup>[1-2]</sup>. Particularly, when the MKR structure is combined with functional two-dimensional materials, a large panel of devices can be achieved via the investigation of variations in resonance properties.<p> </p> Here, a layered metal dichalcogenide semiconductor tin disulfide (SnS<sub>2</sub>), characterized with high intrinsic electron mobility and strong absorption in the visible light regime <sup>[3]</sup>, is chosen to be coated onto MKR. The all-optical control of light functionality is demonstrated in MKR with SnS<sub>2</sub> structure where the signal light power is controlled by the external violet pump power via the absorption property of SnS<sub>2</sub>. The device fabrication, characterization and obtained experimental results will be presented in the talk.

Light control-light characteristics of a micro fiber (MF) coated with tungsten disulfide (WS2) nanosheets is demonstrated in this paper. A device with WS<sub>2</sub>-coated MF has been fabricated, and the transmitted optical powers of the device are measured with 405 and 660 nm pump lasers. By tuning the pump lasers, we achieve the all light controllable sensing of WS<sub>2</sub>-coated MF over a broadband wavelength range from 1520 to 1620 nm, offering competitive sensities of 0.238 and 0.136 dB/mW for 405 and 660 nm pump lasers, respectively. In addition, The rise and fall times of the transient response to pump lasers are also measured. For the 405 nm laser, the rise and fall times of the transient response are 0.32s and 0.42s, respectively. For 660 nm laser, the response times toward the presence (removal) of the pump light transient response are 0.28s and 0.37s, respectively. Experimental results indicate that the device integrated with WS<sub>2</sub> could hold promising potentials in photoelectric and photonic applications.

We demonstrated strain sensing of a microfiber with a microarched transition region, which was fabricated by flame heated tapering. Due to multimode interference of different propagation modes of microfiber, two main transmission dips were observed at 1215.0 and 1469.8 nm. Enhanced by the microarched transition region, the depth of the dip was up to 19 dB at 1215.0 nm. The position of the dip red-shifted while the axial strain changed from 0 to 1166.2 μϵ. The axial strain sensitivity was up to 56.6 pm/μϵ, which was one order of magnitude higher than that of the traditional optical strain sensor based on microfiber or fiber Bragg grating. The linear correlation coefficient was 98.21%. This kind of microfiber with a microarched transition region can be widely used in various physical, chemical, and biological sensing and detection fields.

In this paper, we report a new filter by combining fiber-optic microring and lithium niobate microwaveguide chip. In our design, fiber-optic microring works as a resonator to trapped the resonant light and enlarge its optical energy. The lithium niobate microwaveguide chip serves as a mount to load the fiber-optic microring on the microwaveguide. Then the resonant light coupled from the microring could transmit through the microwaveguide and be detected. We experimentally demonstrated our design and its operation feasibility. The characteristic of the filter could be clearly observed. The results proved that the combination of fiber-optic microring and lithium niobate microwaveguide chip might provide an alternative way to integrate the fiber-optic micro and nanodevices on lithium niobate microwaveguide chip.

We demonstrated temperature sensing of a side-polished fiber with polymer nanoporous film cladding, which was constructed by dehydrating dichromate gelatin film on the polished surface. Due to intermodal interference of core mode and cladding mode, two main transmission valleys were observed at 1219.2 and 1373.2 nm. The modulation amplitudes are ∼8 and 12 dB, respectively. These two transmission valleys show significant sensitivity to the temperature. At the wavelength of 1373.2 nm, the position of transmission valley blueshifted 114 nm while the temperature changes from 30°C to 90°C, and the sensitivity of temperature was up to 1.92 nm/°C. The linear correlation coefficient was 98.67%. The temperature sensing characteristics of nanoporous cladding fiber was successfully demonstrated, and it shows a high potential in photonics applications.

We established a theoretical model for a single knot-ring resonator and investigated the transmission spectrum by Jones matrix. The numerical results show that two orthogonal polarization modes of knot-ring, which are originally resonated at the same wavelength, will split into two resonant modes with different wavelengths. The mode splitting is due to the coupling between the two orthogonal polarization modes in the knot-ring when the twisted angle of the twist coupler is not exactly equal to 2mπ (m is an integer). It is also found that the separation of the mode splitting is linearly proportional to the deviation angle δθ with a high correlation coefficient of 99.6% and a slope of 3.17 nm/rad. Furthermore, a transparency phenomenon analogous to coupled-resonator-induced transparency was also predicted by the model. These findings may have potential applications in lasers and sensors.

A novel type of coreless side-polished fiber (CSPF) was investigated numerically and experimentally for sensing refractive index (RI). Numerical simulations and experiments found that multi-mode interference can be excited at the transitional section of coreless side-polished fiber, leading to resonant dips in transmission spectrum through such a CSPF. A red shift of such dips was observed due to increase in surrounding RI, whereby the CSPF can be used as RI sensor. Interestingly, by such a simple CSPF structure, ultra-high sensitivity of 7225nm/RIU for RI range of 1.432 to 1.434 was achieved in our experiment. As the CSPF can act as a versatile platform, the high sensitivity of the CSPF will open new opportunities for other high sensitive sensors and fiber devices.

Because of high surface-to-volume ratio, few layers MoS<sub>2</sub> material as a kind of 2D materials has been attracted more attention nowadays to be used for photonics devices. We investigated the performance of few-layer MoS<sub>2</sub> when it is covered on a side polished fiber (SPF) to sense relative humidity (RH) of environments. The SPF was made by wheel side polishing method. The few layers MoS<sub>2</sub> was deposited on the side polished surface to be a sensing material. As the environmental humidity changes, the output optical power of the all fiber sensor will change due to the interaction between evanescent field of fiber and MoS<sub>2</sub> material. The change of output power of fiber sensor can reach 16.67dB in the relative humidity range of 40-85%. Experiments using the fiber sensor on human breathing have been made and the respondence has achieved. The experiments showed that the fiber sensor can be used in medical instruments. Key words: fiber sensor, side-polished fiber, humidity sensing, 2D material, MoS<sub>2</sub>.

This study reports on the development and testing of a cost- and time-effective means to optimize a double-sided hemispherical patterned sapphire substrate (PSS) for highly efficient flip-chip GaN-based light-emitting diodes (LEDs). A simulation is conducted to study how light extraction efficiency (LEE) changed as a function of alteration in the parameters of the unit hemisphere for LEDs that are fabricated on a hemispherical PSS. Results show that the LEE of LED flip chip could be enhanced with the optimized hemispherical PSS by over 0.508 and is ∼115.3% higher than that of flip-chip LEDs with non-PSS. This study confirms the high efficiency and excellent capability of the optimized hemispherical PSS pattern to improve LED efficacy.

The organic acetone vapor sensing characteristics of side-polished fiber coating with cholesteric liquid crystal film were investigated. The cholesteric liquid crystal used in our experiments is a mixture compound, which contains 30% cholesteryl oleyl carbonate, 60% cholesteryl pelargonat, and 25% cholesteryl chloride. When cholesteric liquid crystal film was coated on the surface of side-polished fiber, an interference transmission spectrum of fiber could be observed. When the fiber is exposing in acetone vapor, a blue shift of the interference spectrum was found. The higher concentration of acetone vapor is, the larger blue shift of spectrum is found. The shift of transmission spectrum is linear to the concentration of acetone vapor. The sensitivity is 1.356nm/vol% when the concentration of acetone vapor ranges from 3vol% to 16vol%. This study demonstrates a new all-fiber low-cost and portable acetone vapor sensor. It can be also used to investigate the helical structure and molecular orientation of cholesteric liquid crystal.

Sensing the nanometric displacement of a micro-/nano-fiber induced by optical forces is a key technology to study optical forces and optical momentum. When the gap between a micro-/nano-fiber and glass substrate becomes down to micrometer scale or less, a white light interference was observed. The gap changes when optical force arising from the propagating pump light along the micro-/nano-fiber causes a transversal nanometric displacement of a micro-/nanofiber, resulting in movement of the interferometric fringes. Therefore this movement of the interferometric fringes can be used to sense the nanometric displacement of the micro-/nano-fiber induced by optical forces. Experimental results show that the resolutions of this method can reach 7.27nm/pixel for tilted angle 0.8<sup>o</sup> between the micro-/nano-fiber and substrate. It is concluded that the white light interferometry method is suitable for measuring the weak optical force.

A temperature fiber sensor with nanostructured cladding composed ted by titanium dioxide (TiO2) nanoparticles was demonstrated. The nanoparticles self-assembled onto a side polished optical fiber (SPF). The enhancement of interaction between the propagating light and the TiO2 nanoparticles (TN) can be obtained via strong evanescent field of the SPF. The strong light–TN interaction gives rise to temperature sensing with a optical power variation of ~4dB in SPF experimentally for an environment temperature ranging from -7.8°C to 77.6°C. The novel temperature sensor shows a sensitivity of ~0.044 dB/°C. The TN-based fiber-optic temperature sensor is facile to manufactured, compatible with fiber-optic interconnections and high potential in photonics applications.

A method of fabricating three dimensional (3D) microstructured fiber is presented. Polystyrene (PS) microspheres were coated around the surface of a micro-fiber through isothermal heating evaporation induced self-assembly method. Scanning electron microscopy (SEM) image shows that the colloidal crystal has continuous, uniform, and well-ordered face-centered cubic (FCC) structure, with [111] crystallographic direction normal to the surface of micro-fiber. This micro-fiber with three-dimensional photonic crystals structure is very useful in the applications of micro-fiber sensors or filters.

We have investigated the influence of side-polished multimode fiber (SPMMF) core diameters D and residual radius R (the minimum distance between side-polished surface and the center of multimode fiber) on the sensitivity of a SPMMF based refractometer. We show that the residual radius has significant influence on the refractive index (RI) sensitivity but the core diameter does not. A refractometer with a lower SPMMF core diameter has a higher sensitivity. Experimental investigations achieved a maximum sensitivity of 42.23 dB/RIU (refractive index unit) for a refractive index range from 1.300 to 1.440 for a refractometer with a SPMMF core diameter of 50 μm.

A novel all fiber-optic power sensor of violet laser based on methyl blue-functionalized reduced graphene oxide (MB-rGO) film coated on a microfiber (MF) was proposed. The experiments show that when the violet laser illuminating onto the MB-rGO film with power variation from 0.03mw to 12.8mw, the transmitted optical power of the MF changes with a relative variation of ~2.7dB. The novel power sensor of violet laser possesses a sensitivity of ~0.22dB/mw in 1550nm. Furthermore, the MB-rGO-based all fiber-optic violet power sensor is easy to fabricate, compatible with fiberoptic systems and possesses high potentiality in photonics applications such as all fiber-optic broadband sensors, switches and modulators.

In this paper, we propose and analytically demonstrate a novel photonic crystal metallic structure, where a photonic crystal (PC) structure is integrated in a total-internal-reflection (TIR) geometry. This unique configuration introduces a new plasmon excitation mechanism, and the excited plasmon modes satisfy the conditions for both resonance modes in PC structure and Plasmon modes in the metallic structure, which makes it possesses a narrow resonance width, smaller minimum reflectance and higher sensitivity comparing with the conventional SPR sensor. The novel and sensitive PC-metallic biosensor will serve as a promising choose for optical biosensing, and in enhanced total-internal-reflection fluorescence microscopy (TIRFM).

A novel all fiber-optic temperature sensor based on graphene film coated on a side polished fiber (SPF) was
demonstrated. Significantly enhanced interaction between the propagating light and the graphene film can be achieved
via strong evanescent light of the SPF. The experiments shows that the strong interaction results in temperature sensing
with a dynamic optical power variation of 11.3dB in SPF. The novel temperature fiber sensor possesses a linear
correlation coefficient of 99.4%, a sensitivity of 0.13dB/&deg;C, a precision of better than 0.03&deg;C. Furthermore, the
graphene-based all fiber-optic temperature sensor is easy to fabricate, compatible with fiber-optic systems and possesses
high potentiality in photonics applications such as all fiber-optic temperature sensing network.

We report on photonic crystal electro-optic devices formed in engineered thin film lithium niobate (TFLN&trade;) substrates.
Photonic crystal devices previously formed in bulk diffused lithium niobate waveguides have been limited in performance by the depth and aspect ratio of the photonic crystal features. We have overcome this limitation by implementing enhanced etching processes in combination with bulk thin film layer transfer techniques. Photonic crystal
lattices have been formed that consist of hexagonal or square arrays of holes. Various device configurations have been
explored, including Fabry Perot resonators with integrated photonic crystal mirrors and coupled resonator structures. Both theoretical and experimental efforts have shown that device optical performance hinges on the fidelity and sidewall profiles of the etched photonic crystal lattice features. With this technology, very compact photonic crystal sensors on the order of 10 &mu;m x 10 &mu;m in size have been fabricated that have comparable performance to a conventional 2 cm long bulk substrate device. The photonic crystal device technology will have broad application as a compact and minimally invasive probe for sensing any of a multitude of physical parameters, including electrical, radiation, thermal and chemical.

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